Heating apparatus and method



April 12, 1938. w. F; MOORE 2,114,269

HEATING APPARATUS AND METHOD Filed July 2, 19:52 2 Sheets-Sheet 1 FIG.1.

INVENTOR MUM mam ATTORNEY April 12, 1938. w. F. MOORE HEATING APPARATUS AND METHOD 2 Sheets-Sheet 2 Filed July 2; 1932 F IG. 2.

INVENTOR ama/4 M ATTORNEY Patented Apr. 12, 1938 UNITED STATES PATENT OFFICE Gasoline Products Company, Inc.,

Newark,

N. J., a corporation of Delaware Application July 2, 1932, Serial No. 620,629

Claims.

This invention relates in general to heating apparatus and more particularly to a vertical tube furnace having a soaking section therein for use in processes involving the heating of In vertical tube furnaces employing a vertical draft, the heating tubes are arranged in parallel to one another and surround the heating medium. This is for the purpose of uniformly heating the fluid, such as a hydrocarbon oil, passing through the tubes by radiant heat. While'the fluid passing through the tubes is uniformly heated and raised to a'high temperature, it is desirable in some instances to maintain the heated fluid at the high temperature for a longer period in the furnace. Such is particularly the case in the cracking of hydrocarbon oils where it is advantageous to maintain the oil at a conver-' sion temperature in the furnace for a period sufficiently long to allow a maximum amount of conversion of the entire body of oil passing through the heating tubes.

An object of my invention is to provide a furnace having a soaking section in which the heated fluid is maintained at the desired temperature for a period longer than is required to raise the fluid to the said desired temperature.

Another object of my invention is to provide a furnace having a heating chamber divided into radiant and convection heating sections by an upwardly extending wall.

A further object of my invention is to provide a furnace for heating fluid's in which the hot gases of combustion from the radiant heating section are cooled before entering a soaking section by passage through an air preheater.

Still another object of my invention is to provide a furnace in which the heat from the hot products of combustion is efliciently and completely utilized.

With these and other objects in view, which may be incident to my improvements, the invention consists in the parts and combinations and the several method steps to be hereinafter set forth and claimed, with the understanding that the procedure of the several necessary elements may be varied without departing from the spirit and scope of the appended claims.

The invention comprehends the provision of a vertical draft furnace having a plurality of vertical tubes positioned in the heating chamber. The rows of tubes may be each equidistant from the center of the furnace and arranged in a man-' ner to provide a space'between two rows of the tubes. A separating wall of suitable heat insulating material and corresponding to the shape of the interior of the heating chamber may be positioned behind the inner row of tubes and may extend upwardly from the bottom wall of the heating chamber to a point near the top thereby providing a passage for the combustion gases. This separating wall and the vertical walls of the furnace define a convection heating zone or soaking section for the hot gases from the radiant heating zone.

A refractory well having burners therein may be located below the bottom wall of the heating chamber and arranged in such a manner as to cause the hot products of combustion emanating therefrom to extend upwardly in the center of the furnace to uniformly heat the full length of tubes without impingement of the flame on any part of the tubes. The hot products of combustion pass'through the passage between the top of the furnace chamber and the top of the' separating wall and are conducted through the convection heating zone.

In order to cool the combustion gases passing to the convection zone, a suitable air preheater may be located in the passage in such a manner that the hot products of combustion passing to the convection zone are conducted therethrough to heat air to be burned with the fuel in the flre box. The convection gases maintain the fluid passing through the soaking tubes in the convection heating zone at the desired temperature and are withdrawn from the furnace through asuitable flue in which a primary air heater is positioned.

In order to make my invention more -clearly understood, I have shown in the accompanying drawings, means for carrying the same into practical effect without limiting the improvements in their useful applications to the particular constructions which, for the purpose of explanation, have been made the subject of illustration.

Figure 1 is an elevational view, partly in section, of a furnace embodying my invention.

Figure 2 is a sectional view taken along lines 2-2 of Figure 1.

Referring to the drawings wherein the same parts are designated by like characters, there is shown a vertical draft furnace of the upshot type having a vertical tube section I and a fire box 2. A suitable base 3 is provided to support the flre box 2 and any suitable metal framework may support the tube chamber l. The vertical tube section I comprises refractory bottom, top and side walls, the side wall having a suitable insulating lining 5 and the bottom wall 8 and the top wall 1 being of suitable heat insulating material. The tube section .I is divided into a radiant heating section 8 and a convection heating or soaking section 9 by means of an' upwardly extending wall ll of suitable heat insulating material. The wall ll conformsto the shape of the interior of the tube section, which is shown to be cylindrical, and extends from the bottom wall 6 to a point near the top, there being provided a passage l2 between the top wall I and the top of the wall H. The purpose of the space or passage I2 will hereinafter appear.

In the soaking section I, a plurality of rows of tubes i3 are mounted, and may be supported from the bottom wall 8 by any suitable means. By supporting the tubes from the bottom wall, the heavy construction necessary at the top of the furnace to support the-weight of the tubes when suspended therefrom is eliminated. With this arrangement, the vertical tubes are capable of longitudinal expansion and contraction the same as if they were supported from the top of the furnace. The tubes l3 may be connected in parallel or in series or in groups connected in multiple and these groups then connected in series. The tubes may be connected together by suitable juncture boxes I engaging the ends of each tube. Anytype of juncture box may be employed, it being preferred to use one having removable plugs for allowing easy access to the tubes for cleaning purposes. The juncture boxes II are located outside of the convection heating section 9 and are enclosed in suitable chambers l5 having removable covers iii to allow access within the chambers. Both the top and bottom ends of the tubes it are connected by means of the juncture box H, enclosed in the chambers IS, with the upper ends passing through openings, .not shown, in the top wall I so that the tubes may expand or contract 'freely in a vertical direction due to heat variations.

A'row of tubes! 1 is located in the radiant heating section 8 and is positioned adjacent the separating wall ll. In'this manner the side of the tubes adjacent the wall II will receive any heat radiated therefrom. The upper ends of the tubes I! also pass through openings in the top wall I to permit the tubes to expand and contract and are supported by any suitable means at the lower ends thereof. The upper and lower ends of each tube are connected to the corresponding ends of adjacent tubes by suitable return bends positioned in the chambers l8. The chambers l8 are similar for both the upper and lower ends of the tubes and each is provided with a removable cover ill to permit easy access to the return bends so that they may be removed before cleaning or removing the tubes.

As is clearly shown in Figure l, the fire box 2 is located below the bottom wall 6. A refractory well 2| is positioned within the flre box 2 and extends upwardly to the bottom wall 6. The well 2lmay be of frustro conical shape, as shown, or cylindrical in shape, to cause the flame or hot products of combustion formed therein to pass upwardly in a substantial uniform volume throughout the length of the radiant heating section. The refractory material for forming the well 2i may be supported by a suitable shell 22 of heat resistant metal.

Arranged tangentially to the well 2 I and located near the bottom thereof are a plurality of burners 23. The burners 23 are connected to a suitable conduit or ring 24 surrounding the well. A pipe 25 conducts the fuel supply, which may be gas, liquid or powdered fuel from any suitable source of supply to the conduit 24 from which it is introduced into plurality of burners 28. Air which has been preheated, as will be hereinafter explained, enters the fire box 2 through an inlet conduit 26. The air in entering the flre box will pass upwardly into the lower end of the well 2| By providing a well for receiving the fuel and air to be burned, a suflicient and complete initial combustion is accomplished and as a result, the size of the flame column or the hot products of combustion passing upwardly will be substantially the same at the lower part of the radiant heating section 8 as it will be at a point somewhat above the lower wall 6. In this manner, the lower portion of the tubes II will receive substantially the same amount of radiated heat as the other parts and consequently each tube will be heated uniformly throughout its length.

The hot products of combustion passing upwardly in the radiant heating section I are conducted through the passage l2 to the convection heating section 9. Any suitable deflector may be positioned in the top of the heating chamber 8 to create an even flow of the combustion gases passing through the passage l2. An air preheater 21 is positioned in the passageway i2 and suitably supported from the top wall I. The hot products of combustion pass through pipes 28 in the air preheater to heat the air being introduced into the fire box 2. The air to be heated is introduced into the air preheater through an inlet 29 and passes around the pipes 28 thereby creating the necessary turbulence thereof. As will be noted from Figure 2, the air in entering the air preheater 2'! comes in contact with a battle 3| and divides, a portion going in one direction and the other portion in another direction. The two portions of air are heated by indirect heat exchange with the hot productsv of combustion passing through the pipes 28 and leave through an outlet pipe 32. The outlet pipe 32 is suitably connected by means of a pipe 83 to the inlet conduit 26 leading into the fire box 2 where the heated air is intrduced as already explained. While I have shown the air preheater 21 as being located in the passageway l2, it is to be understood that it may be positioned in front of the portion of the tubes l'l surrounding the passage l2. In this manner the air preheater would temper the hot gases before they come in contact with the upper portions of the tubes thereby avoiding the possibility of injury to the tubes by contact with excessively hot gases.

The convection gases passing through the soaking section 2 are withdrawn through a suitable flue 34 and passed to a stack 35 in order to conduct them to the atmosphere. As a means for further utilizing the remaining heat of the gases passing through the flue 34, I have shown a prinary preheating. The air in leaving the primary air heater 35 is conducted through a suitable conduit 31 to the inlet pipe 29 of the air heater 21. While I have shown the conduit 31 passing through the sidewall of the furnace, it is to be understood that it might be passed through the top wall 1 without departing-from my invention. Furthermore the primary air heater may be eliminated and only the air heater 2'! used for heating the air. Any suitable fan or blower may be used to circulate the air through the air heating apparatus.

In accordance with this invention there is prothis arrangement it is possible to accomplish at a constant conversion temperature for a period as long or longer than is required to raise the temperature of the fluid to its conversion temperature.

While my invention has been illustrated as applied to a furnace of the upshot type, it is to be understood that it is equally applicable to a. furnace of the type in which the hot products of combustion are introduced into the heating chamber from the upper part of the furnace. Moreover my invention is not limited to a cylindrical shaped heating apparatus as obviously other shaped furnaces may be used without departing from the spirit thereof.

In operating my furnace in conjunction with other apparatus for carrying out a cracking process, the oil in passing through the tubes in the radiant heating section is raised to a high or cracking temperature. The hot products of com bustion passing upwardly in the radiant heating section will vary from, say, 1500" to 1350 F. while these gases after passing through the air preheater will have a temperature of from, say 1200" to 900 F. The temperature of the gases being delivered to the soaking section is controlled by the quantity of air being heated in the air preheater and from this control the temperature of the oil passing through the soaking section is regulated.

While I have shown and described the preferred embodiment of my invention, I wish it to be understood that I do not confine myself to the precise details of construction herein set forth, by way of illustration, as it is apparent that many changes and variations may be made therein, by

those skilled in the art, without departing from I the spirit of the invention, or exceeding the scope It broadly compreproviding a passage for combustion gases between the top thereof and the top of the heating chamber, heat absorbing tubes in the heating sections, those in the radiant heating sectionbeing heated preponderantly by radiant heat, an air preheater in said passage adapted to cool said combustion 'gases prior 'to their passage to the convection heating section, and means for conducting the heated air to the combustion means.

2. A furnace for heating fluids comprising a vertical heating chamber, a well below said heating chamber having burners therein, said well being adapted to cause the hot products of combustion produced therein by burning fuel with air to extend upwardly in substantially uniform volume, means within said heating chamber to divide same into a radiant heating section and a convection heating section, heat absorbing tubes in the heating sections, those in the radiant heating section being heated preponderantly by radiant heat, an air preheater between the radiant and convection heating sections adapted to cool the combustion gases immediately upon leaving the radiant heating section and prior to their passage to the convection heating section and means for conducting preheated air from said air preheater to said well.

3. A furnace for heating fluids comprising a vertical heating chamber, a well below said heating chamber having burners therein,.said well being adapted to cause the hot products of combustion produced therein to extend upwardly in substantially uniform volume, means within said heating chamber to divide same into a radiant heating section and a convection heating section, heat absorbing tubes in the heating sections, those in the radiant heating section being heated pre ponderantly by radiant heat, an air preheater between the radiant and convection heating sections adapted to cool the combustion gases immediately upon leaving the radiant heating section and prior to their passage to the convection heating section, and means for conducting the heated air from the air preheater to the well to aid combustion therein.

4. In a furnace for heating fluids, a radiant heating section and a convection heating section separated by a wall having a passage therethrough, heat absorbing tubes in the radiant and convection heating sections, those in the radiant heating section being heated preponderantly by radiant heat combustion means for supplying heat to the tubes, an air preheater in said passage for heating air adapted to cool the combustion gases immediately upon leaving the radiant heating section and prior to their passage through the convection heating section and means for supplying said heated air from said air preheater to said first-mentioned means.

5. In a furnace for heating hydrocarbon fluids, a radiant heating section and a soaking section, said sections being separated by a wall having a passage therethrough, heat absorbing tubes in both sections, combustion means for supplying heat to said tubes, the number of tubes in the soaking section being greater than the number of tubes in the radiant heating section so that the hydrocarbon fluid being heated is main'tained at a substantially constant temperature in the soaking section for a longer period of time than is required in raising'the temperature of the hydrocarbon fluid in the radiant heating section and an air preheater in said passage adapted to cool the combustion gases prior to their passage to the soaking section.

6. In a furnace for heating hydrocarbon fluids, a radiant heating section and a soaking section, said sections being separated by a wall having a passage therethrough, a row of tubes in the radiant heating section and a-plurality of rows of tubes in the soaking section, combustion means for supplying. heat to said tubes, the combustion gases for the soaking section passing through said passage, the plurality of rows of tubes in the soaking section causing the hydrocarbon fluid being passed therethrough to be subjected to a substantially constant soaking temperature for a longer period than is required in raising the temperature of the hydrocarbon fluid in theradiant heating section and an air preheater in said passage adapted to cool the combustion gases passing to the soaking section. I

7. A furnace for heating fluids comprising a heating chamber, combustion means for heating said chamber, a wall within said chamber to divide same into radiant and convection heating sections, said wall providing a passage for combustion gases between the top thereof and the top of the heating chamber, heat absorbing tubes in the heating sections, those in the radiant heating section being heated preponderantly by radiant heat and an air preheater in said passage adapted to cool the combustion gases from the radiant heating section prior to their passage to the convection heating section.

8. The method of heat treating hydrocarbon fluids which comprises initially burning fuel with air to form hot products of combustion, passing the hot products of combustion through radiant and convection heating zones in succession wherein said products heat hydrocarbon fluid passing therethrough in a stream of restricted cross-section and reducing the temperature of the products of combustion before passing through the convection heating zone by passing them in indirect heat exchange with air used in burning the fuel to thereby preheat the air.

9. A furnace for heating fluids comprising a vertical heating chamber, means for burning iuel with air for heating said chamber, a vertical wall within said chamber to divide same into a radiant heating section and a convection heating section, said wall providing a passage for combustion gases between the top thereof and the top of the heating chamber, heat-absorbing tubes in the heating sections, those in the radiant heating section being heated preponderantly by radiant heat, an

air preheater in said passage adapted to cool said combustion gases prior to their passage to the convection heating section and preheat air, and means for conducting the preheated air to said first-mentioned means.

10. In the cracking of hydrocarbon oils, themethod of heating which comprises passing a restricted stream of the oil through a radiant heat zone of a furnace receiving heat from the burning of fuel with preheated air and heating the oil therein to the desired maximum cracking temperature preponderantly by radiant heat, thence passing the oil stream through a convection heat zone of the furnace, passing combustion gases from the radiant heat zone into the convection heat zone as a source of heat for the latter, and altering the heating characteristics of the combustion gases in transit from the radiant heat zone to the convection heat zone by passing them in heat exchange relation with air used in the burning of fuel prior to the use of the combustion gases in the convection zone wherein they maintain the oil at cracking temperature. a 

